Methods and apparatus of residual and coefficients coding

ABSTRACT

An electronic apparatus performs a method of decoding video data. The method comprises: receiving, from bitstream, one or more syntax elements and video data corresponding to a coding unit encoded in palette mode; determining a first binarization parameter according to the one or more syntax elements; decoding, from the video data, a first codeword for an escape sample within the coding unit; decoding, from the video data, a value for an escape sample within the coding unit using a predefined binarization scheme with the first binarization parameter.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of PCT Application No.PCT/US2020/058306, entitled “METHODS AND APPARATUS OF RESIDUAL ANDCOEFFICIENTS CODING” filed on Oct. 30, 2020, which claims priority toU.S. Provisional Patent Application No. 62/929,755, entitled “Residualand Coefficients Coding for Video Coding” filed Nov. 1, 2019, both ofwhich are incorporated by reference in their entireties.

TECHNICAL FIELD

The present application generally relates to video data coding andcompression, and in particular, to method and system of improvement inpalette mode coding for video coding.

BACKGROUND

Digital video is supported by a variety of electronic devices, such asdigital televisions, laptop or desktop computers, tablet computers,digital cameras, digital recording devices, digital media players, videogaming consoles, smart phones, video teleconferencing devices, videostreaming devices, etc. The electronic devices transmit, receive,encode, decode, and/or store digital video data by implementing videocompression/decompression standards as defined by MPEG-4, ITU-T H.263,ITU-T H.264/MPEG-4, Part 10, Advanced Video Coding (AVC), HighEfficiency Video Coding (HEVC), and Versatile Video Coding (VVC)standard. Video compression typically includes performing spatial (intraframe) prediction and/or temporal (inter frame) prediction to reduce orremove redundancy inherent in the video data. For block-based videocoding, a video frame is partitioned into one or more slices, each slicehaving multiple video blocks, which may also be referred to as codingtree units (CTUs). Each CTU may contain one coding unit (CU) orrecursively split into smaller CUs until the predefined minimum CU sizeis reached. Each CU (also named leaf CU) contains one or multipletransform units (TUs) and each CU also contains one or multipleprediction units (PUs). Each CU can be coded in either intra, inter orIBC modes. Video blocks in an intra coded (I) slice of a video frame areencoded using spatial prediction with respect to reference samples inneighboring blocks within the same video frame. Video blocks in an intercoded (P or B) slice of a video frame may use spatial prediction withrespect to reference samples in neighboring blocks within the same videoframe or temporal prediction with respect to reference samples in otherprevious and/or future reference video frames.

Spatial or temporal prediction based on a reference block that has beenpreviously encoded, e.g., a neighboring block, results in a predictiveblock for a current video block to be coded. The process of finding thereference block may be accomplished by block matching algorithm.Residual data representing pixel differences between the current blockto be coded and the predictive block is referred to as a residual blockor prediction errors. An inter-coded block is encoded according to amotion vector that points to a reference block in a reference frameforming the predictive block, and the residual block. The process ofdetermining the motion vector is typically referred to as motionestimation. An intra coded block is encoded according to an intraprediction mode and the residual block. For further compression, theresidual block is transformed from the pixel domain to a transformdomain, e.g., frequency domain, resulting in residual transformcoefficients, which may then be quantized. The quantized transformcoefficients, initially arranged in a two-dimensional array, may bescanned to produce a one-dimensional vector of transform coefficients,and then entropy encoded into a video bitstream to achieve even morecompression.

The encoded video bitstream is then saved in a computer-readable storagemedium (e.g., flash memory) to be accessed by another electronic devicewith digital video capability or directly transmitted to the electronicdevice wired or wirelessly. The electronic device then performs videodecompression (which is an opposite process to the video compressiondescribed above) by, e.g., parsing the encoded video bitstream to obtainsyntax elements from the bitstream and reconstructing the digital videodata to its original format from the encoded video bitstream based atleast in part on the syntax elements obtained from the bitstream, andrenders the reconstructed digital video data on a display of theelectronic device.

With digital video quality going from high definition, to 4K×2K or even8K×4K, the amount of vide data to be encoded/decoded growsexponentially. It is a constant challenge in terms of how the video datacan be encoded/decoded more efficiently while maintaining the imagequality of the decoded video data.

SUMMARY

The present application describes implementations related to video dataencoding and decoding and, more particularly, to method and system ofimprovement in palette mode coding for video coding.

According to a first aspect of the present application, a method ofdecoding video data, the method comprising: receiving, from bitstream,one or more syntax elements and video data corresponding to a codingunit encoded in palette mode; determining a first binarization parameteraccording to the one or more syntax elements; decoding, from the videodata, a first codeword for an escape sample within the coding unit;decoding, from the video data, a value for an escape sample within thecoding unit using a predefined binarization scheme with the firstbinarization parameter.

According to a second aspect of the present application, an electronicapparatus includes one or more processing units, memory and a pluralityof programs stored in the memory. The programs, when executed by the oneor more processing units, cause the electronic apparatus to perform themethod of decoding video data as described above.

According to a third aspect of the present application, a non-transitorycomputer readable storage medium stores a plurality of programs forexecution by an electronic apparatus having one or more processingunits. The programs, when executed by the one or more processing units,cause the electronic apparatus to perform the method of decoding videodata as described above.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the implementations and are incorporated herein andconstitute a part of the specification, illustrate the describedimplementations and together with the description serve to explain theunderlying principles. Like reference numerals refer to correspondingparts.

FIG. 1 is a block diagram illustrating an exemplary video encoding anddecoding system in accordance with some implementations of the presentdisclosure.

FIG. 2 is a block diagram illustrating an exemplary video encoder inaccordance with some implementations of the present disclosure.

FIG. 3 is a block diagram illustrating an exemplary video decoder inaccordance with some implementations of the present disclosure.

FIGS. 4A through 4E are block diagrams illustrating how a frame isrecursively partitioned into multiple video blocks of different sizesand shapes in accordance with some implementations of the presentdisclosure.

FIGS. 5A through 5B are block diagrams illustrating examples oftransform efficient coding using context coding and bypass coding inaccordance with some implementations of the present disclosure.

FIG. 6 is a block diagram illustrating an exemplary process of dependentscalar quantization in accordance with some implementations of thepresent disclosure.

FIG. 7 is a block diagram illustrating an exemplary state machine forswitching between two different scalar quantizers in accordance withsome implementations of the present disclosure.

FIGS. 8A through 8D are block diagrams illustrating examples of usingpalette tables for coding video data in accordance with someimplementations of the present disclosure.

FIG. 9 is a flowchart illustrating exemplary processes by which a videodecoder performs escape sample coding for a coding block in accordancewith some implementations of the present disclosure.

FIG. 10 is a block diagram illustrating an example Context-adaptivebinary arithmetic coding (CABAC) engine in accordance with someimplementations of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to specific implementations,examples of which are illustrated in the accompanying drawings. In thefollowing detailed description, numerous non-limiting specific detailsare set forth in order to assist in understanding the subject matterpresented herein. But it will be apparent to one of ordinary skill inthe art that various alternatives may be used without departing from thescope of claims and the subject matter may be practiced without thesespecific details. For example, it will be apparent to one of ordinaryskill in the art that the subject matter presented herein can beimplemented on many types of electronic devices with digital videocapabilities.

FIG. 1 is a block diagram illustrating an exemplary system 10 forencoding and decoding video blocks in parallel in accordance with someimplementations of the present disclosure. As shown in FIG. 1, system 10includes a source device 12 that generates and encodes video data to bedecoded at a later time by a destination device 14. Source device 12 anddestination device 14 may comprise any of a wide variety of electronicdevices, including desktop or laptop computers, tablet computers, smartphones, set-top boxes, digital televisions, cameras, display devices,digital media players, video gaming consoles, video streaming device, orthe like. In some implementations, source device 12 and destinationdevice 14 are equipped with wireless communication capabilities.

In some implementations, destination device 14 may receive the encodedvideo data to be decoded via a link 16. Link 16 may comprise any type ofcommunication medium or device capable of moving the encoded video datafrom source device 12 to destination device 14. In one example, link 16may comprise a communication medium to enable source device 12 totransmit the encoded video data directly to destination device 14 inreal-time. The encoded video data may be modulated according to acommunication standard, such as a wireless communication protocol, andtransmitted to destination device 14. The communication medium maycomprise any wireless or wired communication medium, such as a radiofrequency (RF) spectrum or one or more physical transmission lines. Thecommunication medium may form part of a packet-based network, such as alocal area network, a wide-area network, or a global network such as theInternet. The communication medium may include routers, switches, basestations, or any other equipment that may be useful to facilitatecommunication from source device 12 to destination device 14.

In some other implementations, the encoded video data may be transmittedfrom output interface 22 to a storage device 32. Subsequently, theencoded video data in storage device 32 may be accessed by destinationdevice 14 via input interface 28. Storage device 32 may include any of avariety of distributed or locally accessed data storage media such as ahard drive, Blu-ray discs, DVDs, CD-ROMs, flash memory, volatile ornon-volatile memory, or any other suitable digital storage media forstoring encoded video data. In a further example, storage device 32 maycorrespond to a file server or another intermediate storage device thatmay hold the encoded video data generated by source device 12.Destination device 14 may access the stored video data from storagedevice 32 via streaming or downloading. The file server may be any typeof computer capable of storing encoded video data and transmitting theencoded video data to destination device 14. Exemplary file serversinclude a web server (e.g., for a website), an FTP server, networkattached storage (NAS) devices, or a local disk drive. Destinationdevice 14 may access the encoded video data through any standard dataconnection, including a wireless channel (e.g., a Wi-Fi connection), awired connection (e.g., DSL, cable modem, etc.), or a combination ofboth that is suitable for accessing encoded video data stored on a fileserver. The transmission of encoded video data from storage device 32may be a streaming transmission, a download transmission, or acombination of both.

As shown in FIG. 1, source device 12 includes a video source 18, a videoencoder 20 and an output interface 22. Video source 18 may include asource such as a video capture device, e.g., a video camera, a videoarchive containing previously captured video, a video feed interface toreceive video from a video content provider, and/or a computer graphicssystem for generating computer graphics data as the source video, or acombination of such sources. As one example, if video source 18 is avideo camera of a security surveillance system, source device 12 anddestination device 14 may form camera phones or video phones. However,the implementations described in the present application may beapplicable to video coding in general, and may be applied to wirelessand/or wired applications.

The captured, pre-captured, or computer-generated video may be encodedby video encoder 20. The encoded video data may be transmitted directlyto destination device 14 via output interface 22 of source device 12.The encoded video data may also (or alternatively) be stored ontostorage device 32 for later access by destination device 14 or otherdevices, for decoding and/or playback. Output interface 22 may furtherinclude a modem and/or a transmitter.

Destination device 14 includes an input interface 28, a video decoder30, and a display device 34. Input interface 28 may include a receiverand/or a modem and receive the encoded video data over link 16. Theencoded video data communicated over link 16, or provided on storagedevice 32, may include a variety of syntax elements generated by videoencoder 20 for use by video decoder 30 in decoding the video data. Suchsyntax elements may be included within the encoded video datatransmitted on a communication medium, stored on a storage medium, orstored a file server.

In some implementations, destination device 14 may include a displaydevice 34, which can be an integrated display device and an externaldisplay device that is configured to communicate with destination device14. Display device 34 displays the decoded video data to a user, and maycomprise any of a variety of display devices such as a liquid crystaldisplay (LCD), a plasma display, an organic light emitting diode (OLED)display, or another type of display device.

Video encoder 20 and video decoder 30 may operate according toproprietary or industry standards, such as VVC, HEVC, MPEG-4, Part 10,Advanced Video Coding (AVC), or extensions of such standards. It shouldbe understood that the present application is not limited to a specificvideo coding/decoding standard and may be applicable to other videocoding/decoding standards. It is generally contemplated that videoencoder 20 of source device 12 may be configured to encode video dataaccording to any of these current or future standards. Similarly, it isalso generally contemplated that video decoder 30 of destination device14 may be configured to decode video data according to any of thesecurrent or future standards.

Video encoder 20 and video decoder 30 each may be implemented as any ofa variety of suitable encoder circuitry, such as one or moremicroprocessors, digital signal processors (DSPs), application specificintegrated circuits (ASICs), field programmable gate arrays (FPGAs),discrete logic, software, hardware, firmware or any combinationsthereof. When implemented partially in software, an electronic devicemay store instructions for the software in a suitable, non-transitorycomputer-readable medium and execute the instructions in hardware usingone or more processors to perform the video coding/decoding operationsdisclosed in the present disclosure. Each of video encoder 20 and videodecoder 30 may be included in one or more encoders or decoders, eitherof which may be integrated as part of a combined encoder/decoder (CODEC)in a respective device.

FIG. 2 is a block diagram illustrating an exemplary video encoder 20 inaccordance with some implementations described in the presentapplication. Video encoder 20 may perform intra and inter predictivecoding of video blocks within video frames. Intra predictive codingrelies on spatial prediction to reduce or remove spatial redundancy invideo data within a given video frame or picture. Inter predictivecoding relies on temporal prediction to reduce or remove temporalredundancy in video data within adjacent video frames or pictures of avideo sequence.

As shown in FIG. 2, video encoder 20 includes video data memory 40,prediction processing unit 41, decoded picture buffer (DPB) 64, summer50, transform processing unit 52, quantization unit 54, and entropyencoding unit 56. Prediction processing unit 41 further includes motionestimation unit 42, motion compensation unit 44, partition unit 45,intra prediction processing unit 46, and intra block copy (BC) unit 48.In some implementations, video encoder 20 also includes inversequantization unit 58, inverse transform processing unit 60, and summer62 for video block reconstruction. A deblocking filter (not shown) maybe positioned between summer 62 and DPB 64 to filter block boundaries toremove blockiness artifacts from reconstructed video. An in loop filter(not shown) may also be used in addition to the deblocking filter tofilter the output of summer 62. Video encoder 20 may take the form of afixed or programmable hardware unit or may be divided among one or moreof the illustrated fixed or programmable hardware units.

Video data memory 40 may store video data to be encoded by thecomponents of video encoder 20. The video data in video data memory 40may be obtained, for example, from video source 18. DPB 64 is a bufferthat stores reference video data for use in encoding video data by videoencoder 20 (e.g., in intra or inter predictive coding modes). Video datamemory 40 and DPB 64 may be formed by any of a variety of memorydevices. In various examples, video data memory 40 may be on-chip withother components of video encoder 20, or off-chip relative to thosecomponents.

As shown in FIG. 2, after receiving video data, partition unit 45 withinprediction processing unit 41 partitions the video data into videoblocks. This partitioning may also include partitioning a video frameinto slices, tiles, or other larger coding units (CUs) according to apredefined splitting structures such as quad-tree structure associatedwith the video data. The video frame may be divided into multiple videoblocks (or sets of video blocks referred to as tiles). Predictionprocessing unit 41 may select one of a plurality of possible predictivecoding modes, such as one of a plurality of intra predictive codingmodes or one of a plurality of inter predictive coding modes, for thecurrent video block based on error results (e.g., coding rate and thelevel of distortion). Prediction processing unit 41 may provide theresulting intra or inter prediction coded block to summer 50 to generatea residual block and to summer 62 to reconstruct the encoded block foruse as part of a reference frame subsequently. Prediction processingunit 41 also provides syntax elements, such as motion vectors,intra-mode indicators, partition information, and other such syntaxinformation, to entropy encoding unit 56.

In order to select an appropriate intra predictive coding mode for thecurrent video block, intra prediction processing unit 46 withinprediction processing unit 41 may perform intra predictive coding of thecurrent video block relative to one or more neighboring blocks in thesame frame as the current block to be coded to provide spatialprediction. Motion estimation unit 42 and motion compensation unit 44within prediction processing unit 41 perform inter predictive coding ofthe current video block relative to one or more predictive blocks in oneor more reference frames to provide temporal prediction. Video encoder20 may perform multiple coding passes, e.g., to select an appropriatecoding mode for each block of video data.

In some implementations, motion estimation unit 42 determines the interprediction mode for a current video frame by generating a motion vector,which indicates the displacement of a prediction unit (PU) of a videoblock within the current video frame relative to a predictive blockwithin a reference video frame, according to a predetermined patternwithin a sequence of video frames. Motion estimation, performed bymotion estimation unit 42, is the process of generating motion vectors,which estimate motion for video blocks. A motion vector, for example,may indicate the displacement of a PU of a video block within a currentvideo frame or picture relative to a predictive block within a referenceframe (or other coded unit) relative to the current block being codedwithin the current frame (or other coded unit). The predeterminedpattern may designate video frames in the sequence as P frames or Bframes. Intra BC unit 48 may determine vectors, e.g., block vectors, forintra BC coding in a manner similar to the determination of motionvectors by motion estimation unit 42 for inter prediction, or mayutilize motion estimation unit 42 to determine the block vector.

A predictive block is a block of a reference frame that is deemed asclosely matching the PU of the video block to be coded in terms of pixeldifference, which may be determined by sum of absolute difference (SAD),sum of square difference (SSD), or other difference metrics. In someimplementations, video encoder 20 may calculate values for sub-integerpixel positions of reference frames stored in DPB 64. For example, videoencoder 20 may interpolate values of one-quarter pixel positions,one-eighth pixel positions, or other fractional pixel positions of thereference frame. Therefore, motion estimation unit 42 may perform amotion search relative to the full pixel positions and fractional pixelpositions and output a motion vector with fractional pixel precision.

Motion estimation unit 42 calculates a motion vector for a PU of a videoblock in an inter prediction coded frame by comparing the position ofthe PU to the position of a predictive block of a reference frameselected from a first reference frame list (List 0) or a secondreference frame list (List 1), each of which identifies one or morereference frames stored in DPB 64. Motion estimation unit 42 sends thecalculated motion vector to motion compensation unit 44 and then toentropy encoding unit 56.

Motion compensation, performed by motion compensation unit 44, mayinvolve fetching or generating the predictive block based on the motionvector determined by motion estimation unit 42. Upon receiving themotion vector for the PU of the current video block, motion compensationunit 44 may locate a predictive block to which the motion vector pointsin one of the reference frame lists, retrieve the predictive block fromDPB 64, and forward the predictive block to summer 50. Summer 50 thenforms a residual video block of pixel difference values by subtractingpixel values of the predictive block provided by motion compensationunit 44 from the pixel values of the current video block being coded.The pixel difference values forming the residual vide block may includeluma or chroma difference components or both. Motion compensation unit44 may also generate syntax elements associated with the video blocks ofa video frame for use by video decoder 30 in decoding the video blocksof the video frame. The syntax elements may include, for example, syntaxelements defining the motion vector used to identify the predictiveblock, any flags indicating the prediction mode, or any other syntaxinformation described herein. Note that motion estimation unit 42 andmotion compensation unit 44 may be highly integrated, but areillustrated separately for conceptual purposes.

In some implementations, intra BC unit 48 may generate vectors and fetchpredictive blocks in a manner similar to that described above inconnection with motion estimation unit 42 and motion compensation unit44, but with the predictive blocks being in the same frame as thecurrent block being coded and with the vectors being referred to asblock vectors as opposed to motion vectors. In particular, intra BC unit48 may determine an intra-prediction mode to use to encode a currentblock. In some examples, intra BC unit 48 may encode a current blockusing various intra-prediction modes, e.g., during separate encodingpasses, and test their performance through rate-distortion analysis.Next, intra BC unit 48 may select, among the various testedintra-prediction modes, an appropriate intra-prediction mode to use andgenerate an intra-mode indicator accordingly. For example, intra BC unit48 may calculate rate-distortion values using a rate-distortion analysisfor the various tested intra-prediction modes, and select theintra-prediction mode having the best rate-distortion characteristicsamong the tested modes as the appropriate intra-prediction mode to use.Rate-distortion analysis generally determines an amount of distortion(or error) between an encoded block and an original, unencoded blockthat was encoded to produce the encoded block, as well as a bitrate(i.e., a number of bits) used to produce the encoded block. Intra BCunit 48 may calculate ratios from the distortions and rates for thevarious encoded blocks to determine which intra-prediction mode exhibitsthe best rate-distortion value for the block.

In other examples, intra BC unit 48 may use motion estimation unit 42and motion compensation unit 44, in whole or in part, to perform suchfunctions for Intra BC prediction according to the implementationsdescribed herein. In either case, for Intra block copy, a predictiveblock may be a block that is deemed as closely matching the block to becoded, in terms of pixel difference, which may be determined by sum ofabsolute difference (SAD), sum of squared difference (SSD), or otherdifference metrics, and identification of the predictive block mayinclude calculation of values for sub-integer pixel positions.

Whether the predictive block is from the same frame according to intraprediction, or a different frame according to inter prediction, videoencoder 20 may form a residual video block by subtracting pixel valuesof the predictive block from the pixel values of the current video blockbeing coded, forming pixel difference values. The pixel differencevalues forming the residual video block may include both luma and chromacomponent differences.

Intra prediction processing unit 46 may intra-predict a current videoblock, as an alternative to the inter-prediction performed by motionestimation unit 42 and motion compensation unit 44, or the intra blockcopy prediction performed by intra BC unit 48, as described above. Inparticular, intra prediction processing unit 46 may determine an intraprediction mode to use to encode a current block. To do so, intraprediction processing unit 46 may encode a current block using variousintra prediction modes, e.g., during separate encoding passes, and intraprediction processing unit 46 (or a mode select unit, in some examples)may select an appropriate intra prediction mode to use from the testedintra prediction modes. Intra prediction processing unit 46 may provideinformation indicative of the selected intra-prediction mode for theblock to entropy encoding unit 56. Entropy encoding unit 56 may encodethe information indicating the selected intra-prediction mode in thebitstream.

After prediction processing unit 41 determines the predictive block forthe current video block via either inter prediction or intra prediction,summer 50 forms a residual video block by subtracting the predictiveblock from the current video block. The residual video data in theresidual block may be included in one or more transform units (TUs) andis provided to transform processing unit 52. Transform processing unit52 transforms the residual video data into residual transformcoefficients using a transform, such as a discrete cosine transform(DCT) or a conceptually similar transform.

Transform processing unit 52 may send the resulting transformcoefficients to quantization unit 54. Quantization unit 54 quantizes thetransform coefficients to further reduce bit rate. The quantizationprocess may also reduce the bit depth associated with some or all of thecoefficients. The degree of quantization may be modified by adjusting aquantization parameter. In some examples, quantization unit 54 may thenperform a scan of a matrix including the quantized transformcoefficients. Alternatively, entropy encoding unit 56 may perform thescan.

Following quantization, entropy encoding unit 56 entropy encodes thequantized transform coefficients into a video bitstream using, e.g.,context adaptive variable length coding (CAVLC), context adaptive binaryarithmetic coding (CABAC), syntax-based context-adaptive binaryarithmetic coding (SBAC), probability interval partitioning entropy(PIPE) coding or another entropy encoding methodology or technique. Theencoded bitstream may then be transmitted to video decoder 30, orarchived in storage device 32 for later transmission to or retrieval byvideo decoder 30. Entropy encoding unit 56 may also entropy encode themotion vectors and the other syntax elements for the current video framebeing coded.

Inverse quantization unit 58 and inverse transform processing unit 60apply inverse quantization and inverse transformation, respectively, toreconstruct the residual video block in the pixel domain for generatinga reference block for prediction of other video blocks. As noted above,motion compensation unit 44 may generate a motion compensated predictiveblock from one or more reference blocks of the frames stored in DPB 64.Motion compensation unit 44 may also apply one or more interpolationfilters to the predictive block to calculate sub-integer pixel valuesfor use in motion estimation.

Summer 62 adds the reconstructed residual block to the motioncompensated predictive block produced by motion compensation unit 44 toproduce a reference block for storage in DPB 64. The reference block maythen be used by intra BC unit 48, motion estimation unit 42 and motioncompensation unit 44 as a predictive block to inter predict anothervideo block in a subsequent video frame.

FIG. 3 is a block diagram illustrating an exemplary video decoder 30 inaccordance with some implementations of the present application. Videodecoder 30 includes video data memory 79, entropy decoding unit 80,prediction processing unit 81, inverse quantization unit 86, inversetransform processing unit 88, summer 90, and DPB 92. Predictionprocessing unit 81 further includes motion compensation unit 82, intraprediction processing unit 84, and intra BC unit 85. Video decoder 30may perform a decoding process generally reciprocal to the encodingprocess described above with respect to video encoder 20 in connectionwith FIG. 2. For example, motion compensation unit 82 may generateprediction data based on motion vectors received from entropy decodingunit 80, while intra-prediction unit 84 may generate prediction databased on intra-prediction mode indicators received from entropy decodingunit 80.

In some examples, a unit of video decoder 30 may be tasked to performthe implementations of the present application. Also, in some examples,the implementations of the present disclosure may be divided among oneor more of the units of video decoder 30. For example, intra BC unit 85may perform the implementations of the present application, alone, or incombination with other units of video decoder 30, such as motioncompensation unit 82, intra prediction processing unit 84, and entropydecoding unit 80. In some examples, video decoder 30 may not includeintra BC unit 85 and the functionality of intra BC unit 85 may beperformed by other components of prediction processing unit 81, such asmotion compensation unit 82.

Video data memory 79 may store video data, such as an encoded videobitstream, to be decoded by the other components of video decoder 30.The video data stored in video data memory 79 may be obtained, forexample, from storage device 32, from a local video source, such as acamera, via wired or wireless network communication of video data, or byaccessing physical data storage media (e.g., a flash drive or harddisk). Video data memory 79 may include a coded picture buffer (CPB)that stores encoded video data from an encoded video bitstream. Decodedpicture buffer (DPB) 92 of video decoder 30 stores reference video datafor use in decoding video data by video decoder 30 (e.g., in intra orinter predictive coding modes). Video data memory 79 and DPB 92 may beformed by any of a variety of memory devices, such as dynamic randomaccess memory (DRAM), including synchronous DRAM (SDRAM),magneto-resistive RAM (MRAM), resistive RAM (RRAM), or other types ofmemory devices. For illustrative purpose, video data memory 79 and DPB92 are depicted as two distinct components of video decoder 30 in FIG.3. But it will be apparent to one skilled in the art that video datamemory 79 and DPB 92 may be provided by the same memory device orseparate memory devices. In some examples, video data memory 79 may beon-chip with other components of video decoder 30, or off-chip relativeto those components.

During the decoding process, video decoder 30 receives an encoded videobitstream that represents video blocks of an encoded video frame andassociated syntax elements. Video decoder 30 may receive the syntaxelements at the video frame level and/or the video block level. Entropydecoding unit 80 of video decoder 30 entropy decodes the bitstream togenerate quantized coefficients, motion vectors or intra-prediction modeindicators, and other syntax elements. Entropy decoding unit 80 thenforwards the motion vectors and other syntax elements to predictionprocessing unit 81.

When the video frame is coded as an intra predictive coded (I) frame orfor intra coded predictive blocks in other types of frames, intraprediction processing unit 84 of prediction processing unit 81 maygenerate prediction data for a video block of the current video framebased on a signaled intra prediction mode and reference data frompreviously decoded blocks of the current frame.

When the video frame is coded as an inter-predictive coded (i.e., B orP) frame, motion compensation unit 82 of prediction processing unit 81produces one or more predictive blocks for a video block of the currentvideo frame based on the motion vectors and other syntax elementsreceived from entropy decoding unit 80. Each of the predictive blocksmay be produced from a reference frame within one of the reference framelists. Video decoder 30 may construct the reference frame lists, List 0and List 1, using default construction techniques based on referenceframes stored in DPB 92.

In some examples, when the video block is coded according to the intraBC mode described herein, intra BC unit 85 of prediction processing unit81 produces predictive blocks for the current video block based on blockvectors and other syntax elements received from entropy decoding unit80. The predictive blocks may be within a reconstructed region of thesame picture as the current video block defined by video encoder 20.

Motion compensation unit 82 and/or intra BC unit 85 determinesprediction information for a video block of the current video frame byparsing the motion vectors and other syntax elements, and then uses theprediction information to produce the predictive blocks for the currentvideo block being decoded. For example, motion compensation unit 82 usessome of the received syntax elements to determine a prediction mode(e.g., intra or inter prediction) used to code video blocks of the videoframe, an inter prediction frame type (e.g., B or P), constructioninformation for one or more of the reference frame lists for the frame,motion vectors for each inter predictive encoded video block of theframe, inter prediction status for each inter predictive coded videoblock of the frame, and other information to decode the video blocks inthe current video frame.

Similarly, intra BC unit 85 may use some of the received syntaxelements, e.g., a flag, to determine that the current video block waspredicted using the intra BC mode, construction information of whichvideo blocks of the frame are within the reconstructed region and shouldbe stored in DPB 92, block vectors for each intra BC predicted videoblock of the frame, intra BC prediction status for each intra BCpredicted video block of the frame, and other information to decode thevideo blocks in the current video frame.

Motion compensation unit 82 may also perform interpolation using theinterpolation filters as used by video encoder 20 during encoding of thevideo blocks to calculate interpolated values for sub-integer pixels ofreference blocks. In this case, motion compensation unit 82 maydetermine the interpolation filters used by video encoder 20 from thereceived syntax elements and use the interpolation filters to producepredictive blocks.

Inverse quantization unit 86 inverse quantizes the quantized transformcoefficients provided in the bitstream and entropy decoded by entropydecoding unit 80 using the same quantization parameter calculated byvideo encoder 20 for each video block in the video frame to determine adegree of quantization. Inverse transform processing unit 88 applies aninverse transform, e.g., an inverse DCT, an inverse integer transform,or a conceptually similar inverse transform process, to the transformcoefficients in order to reconstruct the residual blocks in the pixeldomain.

After motion compensation unit 82 or intra BC unit 85 generates thepredictive block for the current video block based on the vectors andother syntax elements, summer 90 reconstructs decoded video block forthe current video block by summing the residual block from inversetransform processing unit 88 and a corresponding predictive blockgenerated by motion compensation unit 82 and intra BC unit 85. Anin-loop filter (not pictured) may be positioned between summer 90 andDPB 92 to further process the decoded video block. The decoded videoblocks in a given frame are then stored in DPB 92, which storesreference frames used for subsequent motion compensation of next videoblocks. DPB 92, or a memory device separate from DPB 92, may also storedecoded video for later presentation on a display device, such asdisplay device 34 of FIG. 1.

In a typical video coding process, a video sequence typically includesan ordered set of frames or pictures. Each frame may include threesample arrays, denoted SL, SCb, and SCr. SL is a two-dimensional arrayof luma samples. SCb is a two-dimensional array of Cb chroma samples.SCr is a two-dimensional array of Cr chroma samples. In other instances,a frame may be monochrome and therefore includes only onetwo-dimensional array of luma samples.

As shown in FIG. 4A, video encoder 20 (or more specifically partitionunit 45) generates an encoded representation of a frame by firstpartitioning the frame into a set of coding tree units (CTUs). A videoframe may include an integer number of CTUs ordered consecutively in araster scan order from left to right and from top to bottom. Each CTU isa largest logical coding unit and the width and height of the CTU aresignaled by the video encoder 20 in a sequence parameter set, such thatall the CTUs in a video sequence have the same size being one of128×128, 64×64, 32×32, and 16×16. But it should be noted that thepresent application is not necessarily limited to a particular size. Asshown in FIG. 4B, each CTU may comprise one coding tree block (CTB) ofluma samples, two corresponding coding tree blocks of chroma samples,and syntax elements used to code the samples of the coding tree blocks.The syntax elements describe properties of different types of units of acoded block of pixels and how the video sequence can be reconstructed atthe video decoder 30, including inter or intra prediction, intraprediction mode, motion vectors, and other parameters. In monochromepictures or pictures having three separate color planes, a CTU maycomprise a single coding tree block and syntax elements used to code thesamples of the coding tree block. A coding tree block may be an N×Nblock of samples.

To achieve a better performance, video encoder 20 may recursivelyperform tree partitioning such as binary-tree partitioning, ternary-treepartitioning, quad-tree partitioning or a combination of both on thecoding tree blocks of the CTU and divide the CTU into smaller codingunits (CUs). As depicted in FIG. 4C, the 64×64 CTU 400 is first dividedinto four smaller CU, each having a block size of 32×32. Among the foursmaller CUs, CU 410 and CU 420 are each divided into four CUs of 16×16by block size. The two 16×16 CUs 430 and 440 are each further dividedinto four CUs of 8×8 by block size. FIG. 4D depicts a quad-tree datastructure illustrating the end result of the partition process of theCTU 400 as depicted in FIG. 4C, each leaf node of the quad-treecorresponding to one CU of a respective size ranging from 32×32 to 8×8.Like the CTU depicted in FIG. 4B, each CU may comprise a coding block(CB) of luma samples and two corresponding coding blocks of chromasamples of a frame of the same size, and syntax elements used to codethe samples of the coding blocks. In monochrome pictures or pictureshaving three separate color planes, a CU may comprise a single codingblock and syntax structures used to code the samples of the codingblock. It should be noted that the quad-tree partitioning depicted inFIGS. 4C and 4D is only for illustrative purposes and one CTU can besplit into CUs to adapt to varying local characteristics based onquad/ternary/binary-tree partitions. In the multi-type tree structure,one CTU is partitioned by a quad-tree structure and each quad-tree leafCU can be further partitioned by a binary and ternary tree structure. Asshown in FIG. 4E, there are five partitioning types, i.e., quaternarypartitioning, horizontal binary partitioning, vertical binarypartitioning, horizontal ternary partitioning, and vertical ternarypartitioning.

In some implementations, video encoder 20 may further partition a codingblock of a CU into one or more M×N prediction blocks (PB). A predictionblock is a rectangular (square or non-square) block of samples on whichthe same prediction, inter or intra, is applied. A prediction unit (PU)of a CU may comprise a prediction block of luma samples, twocorresponding prediction blocks of chroma samples, and syntax elementsused to predict the prediction blocks. In monochrome pictures orpictures having three separate color planes, a PU may comprise a singleprediction block and syntax structures used to predict the predictionblock. Video encoder 20 may generate predictive luma, Cb, and Cr blocksfor luma, Cb, and Cr prediction blocks of each PU of the CU.

Video encoder 20 may use intra prediction or inter prediction togenerate the predictive blocks for a PU. If video encoder 20 uses intraprediction to generate the predictive blocks of a PU, video encoder 20may generate the predictive blocks of the PU based on decoded samples ofthe frame associated with the PU. If video encoder 20 uses interprediction to generate the predictive blocks of a PU, video encoder 20may generate the predictive blocks of the PU based on decoded samples ofone or more frames other than the frame associated with the PU.

After video encoder 20 generates predictive luma, Cb, and Cr blocks forone or more PUs of a CU, video encoder 20 may generate a luma residualblock for the CU by subtracting the CU's predictive luma blocks from itsoriginal luma coding block such that each sample in the CU's lumaresidual block indicates a difference between a luma sample in one ofthe CU's predictive luma blocks and a corresponding sample in the CU'soriginal luma coding block. Similarly, video encoder 20 may generate aCb residual block and a Cr residual block for the CU, respectively, suchthat each sample in the CU's Cb residual block indicates a differencebetween a Cb sample in one of the CU's predictive Cb blocks and acorresponding sample in the CU's original Cb coding block and eachsample in the CU's Cr residual block may indicate a difference between aCr sample in one of the CU's predictive Cr blocks and a correspondingsample in the CU's original Cr coding block.

Furthermore, as illustrated in FIG. 4C, video encoder 20 may usequad-tree partitioning to decompose the luma, Cb, and Cr residual blocksof a CU into one or more luma, Cb, and Cr transform blocks. A transformblock is a rectangular (square or non-square) block of samples on whichthe same transform is applied. A transform unit (TU) of a CU maycomprise a transform block of luma samples, two corresponding transformblocks of chroma samples, and syntax elements used to transform thetransform block samples. Thus, each TU of a CU may be associated with aluma transform block, a Cb transform block, and a Cr transform block. Insome examples, the luma transform block associated with the TU may be asub-block of the CU's luma residual block. The Cb transform block may bea sub-block of the CU's Cb residual block. The Cr transform block may bea sub-block of the CU's Cr residual block. In monochrome pictures orpictures having three separate color planes, a TU may comprise a singletransform block and syntax structures used to transform the samples ofthe transform block.

Video encoder 20 may apply one or more transforms to a luma transformblock of a TU to generate a luma coefficient block for the TU. Acoefficient block may be a two-dimensional array of transformcoefficients. A transform coefficient may be a scalar quantity. Videoencoder 20 may apply one or more transforms to a Cb transform block of aTU to generate a Cb coefficient block for the TU. Video encoder 20 mayapply one or more transforms to a Cr transform block of a TU to generatea Cr coefficient block for the TU.

After generating a coefficient block (e.g., a luma coefficient block, aCb coefficient block or a Cr coefficient block), video encoder 20 mayquantize the coefficient block. Quantization generally refers to aprocess in which transform coefficients are quantized to possibly reducethe amount of data used to represent the transform coefficients,providing further compression. After video encoder 20 quantizes acoefficient block, video encoder 20 may entropy encode syntax elementsindicating the quantized transform coefficients. For example, videoencoder 20 may perform Context-Adaptive Binary Arithmetic Coding (CABAC)on the syntax elements indicating the quantized transform coefficients.Finally, video encoder 20 may output a bitstream that includes asequence of bits that forms a representation of coded frames andassociated data, which is either saved in storage device 32 ortransmitted to destination device 14.

After receiving a bitstream generated by video encoder 20, video decoder30 may parse the bitstream to obtain syntax elements from the bitstream.Video decoder 30 may reconstruct the frames of the video data based atleast in part on the syntax elements obtained from the bitstream. Theprocess of reconstructing the video data is generally reciprocal to theencoding process performed by video encoder 20. For example, videodecoder 30 may perform inverse transforms on the coefficient blocksassociated with TUs of a current CU to reconstruct residual blocksassociated with the TUs of the current CU. Video decoder 30 alsoreconstructs the coding blocks of the current CU by adding the samplesof the predictive blocks for PUs of the current CU to correspondingsamples of the transform blocks of the TUs of the current CU. Afterreconstructing the coding blocks for each CU of a frame, video decoder30 may reconstruct the frame.

As noted above, video coding achieves video compression using primarilytwo modes, i.e., intra-frame prediction (or intra-prediction) andinter-frame prediction (or inter-prediction). Palette-based coding isanother coding scheme that has been adopted by many video codingstandards. In palette-based coding, which may be particularly suitablefor screen-generated content coding, a video coder (e.g., video encoder20 or video decoder 30) forms a palette table of colors representing thevideo data of a given block. The palette table includes the mostdominant (e.g., frequently used) pixel values in the given block. Pixelvalues that are not frequently represented in the video data of thegiven block are either not included in the palette table or included inthe palette table as escape colors.

Each entry in the palette table includes an index for a correspondingpixel value that in the palette table. The palette indices for samplesin the block may be coded to indicate which entry from the palette tableis to be used to predict or reconstruct which sample. This palette modestarts with the process of generating a palette predictor for a firstblock of a picture, slice, tile, or other such grouping of video blocks.As will be explained below, the palette predictor for subsequent videoblocks is typically generated by updating a previously used palettepredictor. For illustrative purpose, it is assumed that the palettepredictor is defined at a picture level. In other words, a picture mayinclude multiple coding blocks, each having its own palette table, butthere is one palette predictor for the entire picture.

To reduce the bits needed for signaling palette entries in the videobitstream, a video decoder may utilize a palette predictor fordetermining new palette entries in the palette table used forreconstructing a video block. For example, the palette predictor mayinclude palette entries from a previously used palette table or even beinitialized with a most recently used palette table by including allentries of the most recently used palette table. In someimplementations, the palette predictor may include fewer than all theentries from the most recently used palette table and then incorporatesome entries from other previously used palette tables. The palettepredictor may have the same size as the palette tables used for codingdifferent blocks or may be larger or smaller than the palette tablesused for coding different blocks. In one example, the palette predictoris implemented as a first-in-first-out (FIFO) table including 64 paletteentries.

To generate a palette table for a block of video data from the palettepredictor, a video decoder may receive, from the encoded videobitstream, a one-bit flag for each entry of the palette predictor. Theone-bit flag may have a first value (e.g., a binary one) indicating thatthe associated entry of the palette predictor is to be included in thepalette table or a second value (e.g., a binary zero) indicating thatthe associated entry of the palette predictor is not to be included inthe palette table. If the size of palette predictor is larger than thepalette table used for a block of video data, then the video decoder maystop receiving more flags once a maximum size for the palette table isreached.

In some implementations, some entries in a palette table may be directlysignaled in the encoded video bitstream instead of being determinedusing the palette predictor. For such entries, the video decoder mayreceive, from the encoded video bitstream, three separate m-bit valuesindicating the pixel values for the luma and two chroma componentsassociated with the entry, where m represents the bit depth of the videodata. Compared with the multiple m-bit values needed for directlysignaled palette entries, those palette entries derived from the palettepredictor only require a one-bit flag. Therefore, signaling some or allpalette entries using the palette predictor can significantly reduce thenumber of bits needed to signal the entries of a new palette table,thereby improving the overall coding efficiency of palette mode coding.

In many instances, the palette predictor for one block is determinedbased on the palette table used to code one or more previously codedblocks. But when coding the first coding tree unit in a picture, a sliceor a tile, the palette table of a previously coded block may not beavailable. Therefore a palette predictor cannot be generated usingentries of the previously used palette tables. In such case, a sequenceof palette predictor initializers may be signaled in a sequenceparameter set (SPS) and/or a picture parameter set (PPS), which arevalues used to generate a palette predictor when a previously usedpalette table is not available. An SPS generally refers to a syntaxstructure of syntax elements that apply to a series of consecutive codedvideo pictures called a coded video sequence (CVS) as determined by thecontent of a syntax element found in the PPS referred to by a syntaxelement found in each slice segment header. A PPS generally refers to asyntax structure of syntax elements that apply to one or more individualpictures within a CVS as determined by a syntax element found in eachslice segment header. Thus, an SPS is generally considered to be ahigher level syntax structure than a PPS, meaning the syntax elementsincluded in the SPS generally change less frequently and apply to alarger portion of video data compared to the syntax elements included inthe PPS.

FIGS. 5A through 5B are block diagrams illustrating examples oftransform efficient coding using context coding and bypass coding inaccordance with some implementations of the present disclosure.

Transform coefficient coding in VVC is similar to that in HEVC becausethey both use non-overlapped coefficient groups (also called CGs orsubblocks). However, there are also some differences between the twoschemes. In HEVC, each CG of coefficients has a fixed size of 4×4. InVVC Draft 6, the CG size becomes dependent on the TB size. As aconsequence, various CG sizes (1×16, 2×8, 8×2, 2×4, 4×2 and 16×1) areavailable in VVC. The CGs inside a coding block, and the transformcoefficients within a CG, are coded according to pre-defined scanorders.

In order to restrict the maximum number of context-coded bins (CCB) perpixel, the area of a TB and the type of video component (i.e., lumacomponent vs. chroma component) are used to derive the maximum number ofcontext-coded bins (CCB) for the TB. In some embodiments, the maximumnumber of context-coded bins is equal to TB_zosize*1.75. Here, TB_zosizerepresents the number of samples within a TB after coefficient zero-out.Note that the coded sub block flag, which is a flag indicating if a CGcontains non-zero coefficient or not, is not considered for CCB count.

Coefficient zero-out is an operation performed on a transform block toforce coefficients located in a certain region of the transform block tobe set to zero. For example, in the current VVC, a 64×64 TB has anassociated zero-out operation. As a result, transform coefficientslocated outside the top-left 32×32 region of the 64×64 TB are all forcedto be zero. In fact, in the current VVC, for any transform block with asize over 32 along a certain dimension, coefficient zero-out operationis performed along that dimension to force coefficients located beyondthe top-left 32×32 region to be zero.

In transform coefficient coding in VVC, a variable, remBinsPass1, isfirst set to the maximum number of context-coded bins (MCCB) allowed.During the coding process, the variable is decreased by one each timewhen a context-coded bin is signaled. While the remBinsPass 1 is largerthan or equal to four, a coefficient is signaled with syntax elementsincluding sig_coeff_flag, abs_level_gt1_flag, par_level_flag, andabs_level_gt3_flag, all using context-coded bins in the first pass. Therest part of level information of the coefficient is coded with syntaxelement of abs remainder using Golomb-Rice code and bypass-coded bins inthe second pass. When the remBinsPass1 becomes smaller than four whilecoding the first pass, a current coefficient is not coded in the firstpass, but directly coded in the second pass with the syntax element ofdec_abs_level using Golomb-Rice code and bypass-coded bins. After allthe above mentioned level coding, the signs (sign_flag) for all scanpositions with sig_coeff_flag equal to one is finally coded as bypassbins. Such a process is depicted in FIG. 5A. The remBinsPass1 is resetfor every TB. The transition of using context-coded bins for thesig_coeff_flag, abs_level_gt1_flag, par_level_flag, andabs_level_gt3_flag to using bypass-coded bins for the rest coefficientshappens at most once per TB. For a coefficient subblock, if theremBinsPass1 is smaller than 4 before coding its very first coefficient,the entire coefficient subblock is coded using bypass-coded bins.

Unlike in HEVC where a single residual coding scheme is designed forcoding both transform coefficients and transform skip coefficients, inVVC two separate residual coding schemes are employed for transformcoefficients and transform skip coefficients (i.e., residuals),respectively.

For example, it is observed that the statistical characteristics ofresiduals in transform skip mode are different from those of transformcoefficients and there is no energy compaction around low-frequencycomponents. The residual coding is modified to account for the differentsignal characteristics of the (spatial) transform skip residual whichincludes:

(1) no signaling of the last x/y position;

(2) coded_sub_block_flag coded for every subblock except for the DCsubblock when all previous flags are equal to 0;

(3) sig_coeff_flag context modelling with two neighboring coefficients;

(4) par_level_flag using only one context model;

(5) additional greater than 5, 7, 9 flags;

(6) modified rice parameter derivation for the remainder binarization;

(7) context modeling for the sign flag is determined based on left andabove neighboring coefficient values and sign flag is parsed aftersig_coeff_flag to keep all context coded bins together;

As shown in FIG. 5B, syntax elements sig_coeff_flag, coeff_sign_flag,abs_level_gt1_flag, par_level_flag, are coded in an interleaved mannerfrom one residual sample to another in the first pass, followed by abslevel_gtX_flag bitplanes in the second pass, and abs remainder coding inthe third pass.

Pass 1: sig coeff_flag, coeff_sign_flag, abs_level_gt1_flag,par_level_flag

Pass 2: abs _levelgt3 _flag, abs_level_gt5_flag, abs_level_gt7_flag,abs_level_gt9_flag

Pass 3: abs remainder

FIG. 6 is a block diagram illustrating an exemplary process of dependentscalar quantization in accordance with some implementations of thepresent disclosure.

In current VVC, the maximum QP value is extended from 51 to 63, and thesignaling of the initial QP is changed accordingly. The initial value ofSliceQpY can be modified at the slice segment layer when a non-zerovalue of slice_qp_delta is coded. For transform skip block, minimumallowed QP is defined as four because quantization step size becomes onewhen QP is equal to one.

In addition, the scalar quantization used in HEVC is adapted with a newconcept called “dependent scalar quantization”. Dependent scalarquantization refers to an approach in which a set of admissiblereconstruction values for a transform coefficient depends on the valuesof the transform coefficient levels that precede the current transformcoefficient level in reconstruction order. When compared with theconventional independent scalar quantization used in HEVC, theadmissible reconstruction vectors are packed denser in the N-dimensionalvector space (N represents the number of transform coefficients in atransform block). That is, for a given average number of admissiblereconstruction vectors per N-dimensional unit volume, the averagedistortion between an input vector and the closest reconstruction vectoris reduced. The approach of dependent scalar quantization is realizedby: (a) defining two scalar quantizers with different reconstructionlevels and (b) defining a process for switching between the two scalarquantizers.

The two scalar quantizers used, denoted by Q0 and Q1, are illustrated inFIG. 6. The location of the available reconstruction levels is uniquelyspecified by a quantization step size Δ. The scalar quantizer used (Q0or Q1) is not explicitly signaled in the bitstream. Instead, thequantizer used for a current transform coefficient is determined by theparities of the transform coefficient levels that precede the currenttransform coefficient in coding or reconstruction order.

FIG. 7 is a block diagram illustrating an exemplary state machine forswitching between two different scalar quantizers in accordance withsome implementations of the present disclosure.

As illustrated in FIG. 7, the switching between the two scalarquantizers (Q0 and Q1) is realized via a state machine with fourquantizer states (QState). The QState can take four different values: 0,1, 2, 3. It is uniquely determined by the parities of the transformcoefficient levels preceding the current transform coefficient incoding/reconstruction order. At the start of the inverse quantizationfor a transform block, the state is set equal to 0. The transformcoefficients are reconstructed in scanning order (i.e., in the sameorder they are entropy decoded). After a current transform coefficientis reconstructed, the state is updated as shown in FIG. 7, where kdenotes the value of the transform coefficient level.

It is also supported to signal the default and user-defined scalingmatrices. The DEFAULT mode scaling matrices are all flat, with elementsequal to 16 for all TB sizes. IBC and intra coding modes currently sharethe same scaling matrices. Thus, for the case of USER_DEFINED matrices,the number of MatrixType and MatrixType_DC are updated as follows:

MatrixType: 30=2 (2 for intra&IBC/inter)×3 (Y/Cb/Cr components)×5(square TB size: from 4×4 to 64×64 for luma, from 2×2 to 32×32 forchroma)

MatrixType_DC: 14=2 (2 for intra&IBC/inter×1 for Y component)×3 (TBsize: 16×16, 32×32, 64×64)+4 (2 for intra&IBC/inter×2 for Cb/Crcomponents)×2 (TB size: 16×16, 32×32)

The DC values are separately coded for following scaling matrices:16×16, 32×32, and 64×64. For TBs of size smaller than 8×8, all elementsin one scaling matrix are signalled. If the TBs have size greater thanor equal to 8×8, only 64 elements in one 8×8 scaling matrix aresignalled as a base scaling matrix. For obtaining square matrices ofsize greater than 8×8, the 8×8 base scaling matrix is up-sampled (byduplication of elements) to the corresponding square size (i.e. 16×16,32×32, 64×64). When the zeroing-out of the high frequency coefficientsfor 64 -point transform is applied, corresponding high frequencies ofthe scaling matrices are also zeroed out. That is, if the width orheight of the TB is greater than or equal to 32, only left or top halfof the coefficients is kept, and the remaining coefficients are assignedto zero. Moreover, the number of elements signalled for the 64×64scaling matrix is also reduced from 8×8 to three 4×4 submatrices, sincethe bottom-right 4×4 elements are never used.

The selection of probability models for the syntax elements related toabsolute values of transform coefficient levels depends on the values ofthe absolute levels or partially reconstructed absolute levels in alocal neighbourhood.

The selected probability models depend on the sum of the absolute levels(or partially reconstructed absolute levels) in a local neighbourhoodand the number of absolute levels greater than 0 (given by the number ofsig_coeff_flags equal to 1) in the local neighbourhood. The contextmodelling and binarization depends on the following measures for thelocal neighbourhood:

-   -   numSig: the number of non-zero levels in the local        neighbourhood;    -   sumAbs1: the sum of partially reconstructed absolute levels        (absLevel1) after the first pass in the local neighbourhood;    -   sumAbs: the sum of reconstructed absolute levels in the local        neighbourhood    -   diagonal position (d): the sum of the horizontal and vertical        coordinates of a current scan position inside the transform        block

Based on the values of numSig, sumAbs1, and d, the probability modelsfor coding sig_coeff_flag, abs_level_gt1_flag, par_level_flag, andabs_level_gt3_flag are selected. The Rice parameter for binarizing absremainder and dec abs level is selected based on the values of sumAbsand numSig.

In current VVC, reduced 32-point MTS (also called RMTS 32) is based onskipping high frequency coefficients and used to reduce computationalcomplexity of 32-point DST-7/DCT-8. And, it accompanies coefficientcoding changes including all types of zero-out (i.e., RMTS32 and theexisting zero out for high frequency components in DCT2). Specifically,binarization of last non-zero coefficient position coding is coded basedon reduced TU size, and the context model selection for the lastnon-zero coefficient position coding is determined by the original TUsize. In addition, 60 context models are used to code the sig_coeff_flagof transform coefficients. The selection of context model index is basedon a sum of a maximum of five previously partially reconstructedabsolute level called locSumAbsPass1 and the state of dependentquantization QState as follows:

If cIdx is equal to 0, ctxInc is derived as follows:

ctxInc=12*Max(0, QState−1)+Min((locSumAbsPass1+1)>>1,3)+(d<2?8:(d<5?4:0))

Otherwise (cIdx is greater than 0), ctxInc is derived as follows:

ctxInc=36+8*Max(0, QState−1)+Min((locSumAbsPass1+1)>>1, 3)+(d<2?4:0)

FIGS. 8A through 8D are block diagrams illustrating examples of usingpalette tables for coding video data in accordance with someimplementations of the present disclosure.

For palette (PLT) mode signaling, the palette mode is coded as aprediction mode for a coding unit, i.e., the prediction modes for acoding unit can be MODE_INTRA, MODE_INTER, MODE_IBC and MODE_PLT. If thepalette mode is utilized, the pixels values in the CU are represented bya small set of representative color values. The set is referred to asthe palette. For pixels with values close to the palette colors, thepalette indices are signaled. For pixels with values outside thepalette, the pixels are denoted with an escape symbol and the quantizedpixel values are signaled directly.

To decode a palette mode encoded block, the decoder needs to decodepalette colors and indices from the bitstream. Palette colors aredefined by a palette table and encoded by the palette table codingsyntax (e.g., palette_predictor_run, num_signaled_palette entries,new_palette_entries). An escape flag, palette_escape_val_present_flag,is signaled for each CU to indicate if escape symbols are present in thecurrent CU. If escape symbols are present, the palette table isaugmented by one more entry and the last index is assigned to the escapemode. Palette indices of all pixels in a CU form a palette index map andare encoded by the palette index map coding syntax (e.g.,num_palette_indices_minus1, palette_idx_idc,copy_above_indices_for_final_run_flag, palette_transpose_flag,copy_above_palette_indices_flag, palette_run_prefix,palette_run_suffix). An example of palette mode coded CU is illustratedin FIG. 8A in which the palette size is 4. The first 3 samples in the CUuse palette entries 2, 0, and 3, respectively, for reconstruction. The“x” sample in the CU represents an escape symbol. A CU level flag,palette_escape_val_present_flag, indicates whether any escape symbolsare present in the CU. If escape symbols are present, the palette sizeis augmented by one and the last index is used to indicate the escapesymbol. Thus, in FIG. 8A, index 4 is assigned to the escape symbol.

For coding of the palette table, a palette predictor is maintained. Thepalette predictor is initialized at the beginning of each slice wherethe palette predictor is reset to 0. For each entry in the palettepredictor, a reuse flag is signaled to indicate whether it is part ofthe current palette. As shown in FIG. 8B, the reuse flags,palette_predictor_run, are sent. After this, the number of new paletteentries are signaled using exponential Golomb code of order 0 throughthe syntax num_signaled_palette_entries. Finally, the component valuesfor the new palette entries, new_palette_entries[], are signaled. Aftercoding the current CU, the palette predictor is updated using thecurrent palette, and entries from the previous palette predictor whichare not reused in the current palette will be added at the end of newpalette predictor until the maximum size allowed is reached.

For coding the palette index map, the indices are coded using horizontalor vertical traverse scans as shown in FIG. 8C. The scan order isexplicitly signaled in the bitstream using the palette_transpose_flag.

The palette indices are coded using two main palette sample modes:‘INDEX’ and ‘COPY_ABOVE’. In the ‘INDEX’ mode, the palette index isexplicitly signaled. In the ‘COPY_ABOVE’ mode, the palette index of thesample in the row above is copied. For both ‘INDEX’ and ‘COPY_ABOVE’modes, a run value is signaled which specifies the number pixels thatare coded using the same mode. The mode is signaled using a flag exceptfor the top row when horizontal scan is used or the first column whenthe vertical scan is used, or when the previous mode was ‘COPY_ABOVE’.

In some embodiments, the coding order for index map is as follows:First, the number of index values for the CU is signaled using thesyntax num_palette_indices_minus1, which is followed by signaling of theactual index values for the entire CU using the syntax palette_idx_idc.Both the number of indices as well as the index values are coded inbypass mode. This groups the index-related bypass-coded bins together.Then the palette mode (INDEX or COPY_ABOVE) and run are signaled in aninterleaved manner using the syntax copy_above_palette_indices_flag,palette_run_prefix and palette_run_suffix.copy_above_palette_indices_flag is a context coded flag (only one bin),the codewords of palette_run_prefix is determined through the processdescribed in Table 3 below and the first 5 bins are context coded.palette_run_suffix is coded as bypass bin. Finally, the component escapevalues corresponding to the escape samples for the entire CU are groupedtogether and coded in the bypass mode. An additional syntax element,copy_above_indices_for_final_run_flag, is signaled after signaling theindex values. This syntax element, in conjunction with the number ofindices, eliminates the need to signal the run value corresponding tothe last run in the block.

In the reference software of VVC (VTM), dual tree is enabled for I-slicewhich separate the coding unit partitioning for luma and chromacomponents. As a result, palette is applied on luma (Y component) andchroma (Cb and Cr components) separately. If dual tree is disabled,palette will be applied on Y, Cb, Cr components jointly.

TABLE 1 Syntax of palette coding Descriptor palette_coding( x0, y0,cbWidth, cbHeight, startComp, numComps ) {  palettePredictionFinished =0  NumPredictedPaletteEntries = 0  for( predictorEntryIdx = 0;predictorEntryIdx < PredictorPaletteSize[ startComp ] &&  !palettePredictionFinished &&   NumPredictedPaletteEntries[ startComp] < palette_max_size; predictorEntryIdx++ ) {   palette_predictor_runae(v)   if( palette_predictor_run != 1 ) {    if(palette_predictor_run > 1 )    predictorEntryIdx += palette_predictor_run − 1   PalettePredictorEntryReuseFlags[ predictorEntryIdx ] = 1   NumPredictedPaletteEntries++   } else    palettePredictionFinished =1  }  if( NumPredictedPaletteEntries < palette_max_size )  num_signalled_palette_entries ae(v)  for( cIdx = startComp; cIdx < (startComp + numComps); cIdx++ )   for( i = 0; i <num_signalled_palette_entries; i++ )    new_palette_entries[ cIdx ][ i ]ae(v)  if( CurrentPaletteSize[ startComp ] > 0 )  palette_escape_val_present_flag ae(v)  if( MaxPaletteIndex > 0 ) {  num_palette_indices_minus1 ae(v)   adjust = 0   for( i = 0;i <= num_palette_indices_minus1; i++ ) {    if( MaxPaletteIndex −adjust > 0 ) {     palette_idx_idc ae(v)     PaletteIndexIdc[ i ] =palette_idx_idc    }    adjust = 1   }  copy_above_indices_for_final_run_flag ae(v)   palette_transpose_flagae(v)  }  if( treeType != DUAL_TREE_CHROMA &&palette_escape_val_present_flag ) {   if(cu_qp_delta_enabled_flag && !IsCuQpDeltaCoded ) {    cu_qp_delta_absae(v)    if( cu_qp_delta_abs )     cu_qp_delta_sign_flag ae(v)   }  } if( treeType != DUAL_TREE_LUMA && palette_escape_val_present_flag ) {  if( cu_chroma_qp_offset_enabled_flag && !IsCuChromaQpOffsetCoded ) {   cu_chroma_qp_offset_flag ae(v)    if( cu_chroma_qp_offset_flag )    cu_chroma_qp_offset_idx ae(v)   }  }  remainingNumIndices =num_palette_indices_minus1 + 1  PaletteScanPos = 0  log2CbWidth = Log2(cbWidth )  log2CbHeight = Log2( cbHeight )  while( PaletteScanPos <cbWidth*cbHeightt ) {   xC = x0 + TraverseScanOrder[ log2CbWidth ][log2CbHeight ][ PaletteScanPos ] [ 0 ]   yC = y0 + TraverseScanOrder[log2CbWidth ][ log2CbHeight ][ PaletteScanPos ] [ 1 ]   if(PaletteScanPos > 0 ) {    xcPrev = x0 + TraverseScanOrder[ log2CbWidth][ log2CbHeight ][ PaletteScanPos − 1 ][ 0 ]    ycPrev = y0 +TraverseScanOrder[ log2CbWidth ][ log2CbHeight ][ PaletteScanPos − 1 ][1 ]   }   PaletteRunMinus1 = cbWidth * cbHeight − PaletteScanPos − 1  RunToEnd = 1   CopyAboveIndicesFlag[ xC ][ yC ] = 0   if(MaxPaletteIndex > 0 )    if( ( ( !palette_transpose_flag && yC > 0 ) || ( palette_transpose_flag && xC > 0 ) )     && CopyAboveIndicesFlag[xcPrev ][ ycPrev ] = = 0 )     if( remainingNumIndices >0 && PaletteScanPos < cbWidth* cbHeight − 1 ) {     copy_above_palette_indices_flag ae(v)      CopyAboveIndicesFlag[ xC][ yC ] = copy_above_palette_indices_flag     } else {      if(PaletteScanPos = = cbWidth * cbHeight − 1 && remainingNumIndices > 0 )      CopyAboveIndicesFlag[ xC ][ yC ] = 0      else      CopyAboveIndicesFlag[ xC ][ yC ] = 1     }   if (CopyAboveIndicesFlag[ xC ][ yC ] = = 0 ) {    currNumIndices =num_palette_indices_minus1 + 1 − remainingNumIndices    PaletteIndexMap[xC ][ yC ] = PaletteIndexIdc[ currNumIndices ]   }   if(MaxPaletteIndex > 0 ) {    if( CopyAboveIndicesFlag[ xC ][ yC ] = = 0 )    remainingNumIndices −= 1    if( remainingNumIndices > 0 | |CopyAboveIndicesFlag[ xC ][ yC ] !=     copy_above_indices_for_final_run_flag ) {     PaletteMaxRunMinus1 =cbWidth * cbHeight − PaletteScanPos − 1 −      remainingNumIndices −copy_above_indices_for_final_run_flag     RunToEnd = 0     if(PaletteMaxRunMinus1 > 0 ) {      palette_run_prefix ae(v)      if( (palette_run_prefix > 1 ) && ( PaletteMaxRunMinus1 !=       ( 1 << (palette_run_prefix − 1 ) ) ) )       palette_run_suffix ae(v)     }    }  }   runPos = 0   while ( runPos <= PaletteRunMinus1 ) {    xR = x0 + TraverseScanOrder[ log2CbWidth ][ log2CbHeight ][ PaletteScanPos ][ 0 ]    yR = y0 + TraverseScanOrder[ log2CbWidth ][ log2CbHeight ][PaletteScanPos ] [ 1 ]    if( CopyAboveIndicesFlag[ xC ][ yC ] = = 0 ) {    CopyAboveIndicesFlag[ xR ][ yR ] = 0     PaletteIndexMap[ xR ][ yR ]= PaletteIndexMap[ xC ][ yC ]    } else {     CopyAboveIndicesFlag[ xR][ yR ] = 1     if ( !palette_transpose_flag )      PaletteIndexMap[ xR][ yR ] = PaletteIndexMap[ xR ][ yR − 1 ]     else      PaletteIndexMap[xR ][ yR ] = PaletteIndexMap[ xR − 1 ][ yR ]    }    runPos++   PaletteScanPos ++   }  }  if( palette_escape_val_present_flag ) {  for( cIdx = startComp; cIdx < ( startComp + numComps ); cIdx++ )   for( sPos = 0; sPos < cbWidth* cbHeight; sPos++ ) {     xC = x0 +TraverseScanOrder[ log2CbWidth ][ log2CbHeight ][ sPos ][ 0 ]     yC =y0 + TraverseScanOrder[ log2CbWidth ][ log2CbHeight ][ sPos ][ 1 ]    if( PaletteIndexMap[ cIdx ][ xC ][ yC ] = = MaxPaletteIndex ) {     palette_escape_val ae(v)      PaletteEscapeVal[ cIdx ][ xC ][ yC ]= palette_escape_val     }    }  } }

TABLE 2 Semantic of palette coding In the following semantics, the arrayindices x0, y0 specify the location ( x0, y0 ) of the top- left lumasample of the considered coding block relative to the top-left lumasample of the picture. The array indices xC, yC specify the location (xC, yC ) of the sample relative to the top-left luma sample of thepicture. The array index startComp specifies the first color componentof the current palette table. startComp equal to 0 indicates the Ycomponent; startComp equal to 1 indicates the Cb component; startCompequal to 2 indicates the Cr component. numComps specifies the number ofcolor components in the current palette table. The palette predictorconsists of palette entries from previous coding units that are used topredict the entries in the current palette. The variablePredictorPaletteSize[ startComp ] specifies the size of the palettepredictor for the first color component of the current palette tablestartComp. The variable PalettePredictorEntryReuseFlags[ i ] equal to 1specifies that the i-th entry in the palette predictor is reused in thecurrent palette. PalettePredictorEntryReuseFlags[ i ] equal to 0specifies that the i-th entry in the palette predictor is not an entryin the current palette. All elements of the arrayPalettePredictorEntryReuseFlags[ i ] are initialized to 0.palette_predictor_run is used to determine the number of zeros thatprecede a non-zero entry in the array PalettePredictorEntryReuseFlags.It is a requirement of bitstream conformance that the value ofpalette_predictor_run shall be in the range of 0 to (PredictorPaletteSize − predictorEntryIdx ), inclusive, wherepredictorEntryIdx corresponds to the current position in the arrayPalettePredictorEntryReuseFlags. The variable NumPredictedPaletteEntriesspecifies the number of entries in the current palette that are reusedfrom the predictor palette. The value of NumPredictedPaletteEntriesshall be in the range of 0 to palette_max_size, inclusive.num_signaled_palette_entries specifies the number of entries in thecurrent palette that are explicitly signaled for the first colorcomponent of the current palette table startComp. Whennum_signaled_palette_entries is not present, it is inferred to be equalto 0. The variable CurrentPaletteSize[ startComp ] specifies the size ofthe current palette for the first color component of the current palettetable startComp and is derived as follows: CurrentPaletteSize[ startComp] = NumPredictedPaletteEntries + num_signaled_palette_entries The valueof CurrentPaletteSize[ startComp ] shall be in the range of 0 topalette_max_size, inclusive. new_palette_entries[ cIdx ][ i ] specifiesthe value for the i-th signaled palette entry for the color componentcIdx. The variable PredictorPaletteEntries[ cIdx ][ i ] specifies thei-th element in the predictor palette for the color component cIdx. Thevariable CurrentPaletteEntries[ cIdx ][ i ] specifies the i-th elementin the current palette for the color component cIdx and is derived asfollows: numPredictedPaletteEntries = 0 for( i = 0; i <PredictorPaletteSize[ startComp ]; i++ ) if(PalettePredictorEntryReuseFlags[ i ] ) { for( cIdx =startComp; cIdx < (startComp + numComps ); cIdx++ ) CurrentPaletteEntries[ cIdx ][numPredictedPaletteEntries ] = PredictorPaletteEntries[ cIdx ][ i ]numPredictedPaletteEntries++ } for( cIdx = startComp; cIdx <(startComp + numComps); cIdx++) for( i = 0; i <num_signaled_palette_entries[startComp]; i++ ) CurrentPaletteEntries[cIdx ][ numPredictedPaletteEntries + i ] = new_palette_entries[ cIdx ][i ] palette_escape_val_present_flag equal to 1 specifies that thecurrent coding unit contains at least one escape coded sample.escape_val_present_flag equal to 0 specifies that there are no escapecoded samples in the current coding unit. When not present, the value ofpalette_escape_val_present_flag is inferred to be equal to 1. Thevariable MaxPaletteIndex specifies the maximum possible value for apalette index for the current coding unit. The value of MaxPaletteIndexis set equal to CurrentPaletteSize[ startComp ] − 1 +palette_escape_val_present_flag. num_palette_indices_minus1 plus 1 isthe number of palette indices explicitly signaled or inferred for thecurrent block. When num_palette_indices_minus1 is not present, it isinferred to be equal to 0. palette_idx_idc is an indication of an indexto the palette table, CurrentPaletteEntries. The value ofpalette_idx_idc shall be in the range of 0 to MaxPaletteIndex,inclusive, for the first index in the block and in the range of 0 to (MaxPaletteIndex − 1 ), inclusive, for the remaining indices in theblock. When palette_idx_idc is not present, it is inferred to be equalto 0. The variable PaletteIndexIdc[ i ] stores the i-th palette_idx_idcexplicitly signaled or inferred. All elements of the arrayPaletteIndexIdc[ i ] are initialized to 0.copy_above_indices_for_final_run_flag equal to 1 specifies that thepalette indices of the last positions in the coding unit are copied fromthe palette indices in the row above if horizontal traverse scan is usedor the palette indices in the left column if vertical traverse scan isused. copy_above_indices_for_final_run_flag equal to 0 specifies thatthe palette indices of the last positions in the coding unit are copiedfrom PaletteIndexIdc[ num_palette_indices_minus1 ]. Whencopy_above_indices_for_final_run_flag is not present, it is inferred tobe equal to 0. palette_transpose_flag equal to 1 specifies that verticaltraverse scan is applied for scanning the indices for samples in thecurrent coding unit. palette_transpose_flag equal to 0 specifies thathorizontal traverse scan is applied for scanning the indices for samplesin the current coding unit. When not present, the value ofpalette_transpose_flag is inferred to be equal to 0. The arrayTraverseScanOrder specifies the scan order array for palette coding.TraverseScanOrder is assigned the horizontal scan order HorTravScanOrderif palette_transpose_flag is equal to 0 and TraverseScanOrder isassigned the vertical scan order VerTravScanOrder ifpalette_transpose_flag is equal to 1. copy_above_palette_indices_flagequal to 1 specifies that the palette index is equal to the paletteindex at the same location in the row above if horizontal traverse scanis used or the same location in the left column if vertical traversescan is used. copy_above_palette_indices_flag equal to 0 specifies thatan indication of the palette index of the sample is coded in thebitstream or inferred. The variable CopyAboveIndicesFlag[ xC ][ yC ]equal to 1 specifies that the palette index is copied from the paletteindex in the row above (horizontal scan) or left column (vertical scan).CopyAbovelndicesFlag[ xC ][ yC ] equal to 0 specifies that the paletteindex is explicitly coded in the bitstream or inferred. The arrayindices xC, yC specify the location ( xC, yC ) of the sample relative tothe top-left luma sample of the picture. The value of PaletteIndexMap[xC ][ yC ] shall be in the range of 0 to ( MaxPaletteIndex − 1 ),inclusive. The variable PaletteIndexMap[ xC ][ yC ] specifies a paletteindex, which is an index to the array represented byCurrentPaletteEntries. The array indices xC, yC specify the location (xC, yC ) of the sample relative to the top-left luma sample of thepicture. The value of PaletteIndexMap[ xC ][ yC ] shall be in the rangeof 0 to MaxPaletteIndex, inclusive. The variable adjustedRefPaletteIndexis derived as follows: adjustedRefPaletteIndex = MaxPaletteIndex + 1 if(PaletteScanPos > 0 ) { xcPrev = x0 + TraverseScanOrder[ log2CbWidth ][log2bHeight ][ PaletteScanPos − 1 ][ 0 ] ycPrev = y0 +TraverseScanOrder[ log2CbWidth ][ log2bHeight ][ PaletteScanPos − 1 ][ 1] if( CopyAboveIndicesFlag[ xcPrev ][ ycPrev ] = = 0 ) {adjustedRefPaletteIndex = PaletteIndexMap[ xcPrev ][ ycPrev ] { } else {if( !palette_transpose_flag ) adjustedRefPaletteIndex = PaletteIndexMap[xC ][ yC − 1 ] else adjustedRefPaletteIndex = PaletteIndexMap[ xC − 1 ][yC ] } } When CopyAboveIndicesFlag[ xC ][ yC ] is equal to 0, thevariable CurrPaletteIndex is derived as follows: if(CurrPaletteIndex >= adjustedRefPaletteIndex ) CurrPaletteIndex++palette_run_prefix, when present, specifies the prefix part in thebinarization of PaletteRunMinus1. palette_run_suffix is used in thederivation of the variable PaletteRunMinus1. When not present, the valueof palette_run_suffix is inferred to be equal to 0. When RunToEnd isequal to 0, the variable PaletteRunMinus1 is derived as follows: - IfPaletteMaxRunMinus1 is equal to 0, PaletteRunMinus1 is set equal to 0. -Otherwise (PaletteMaxRunMinus1 is greater than 0) the followingapplies: - If palette_run_prefix is less than 2, the following applies:PaletteRunMinus1 = palette_run_prefix - Otherwise (palette_run_prefix isgreater than or equal to 2), the following applies: PrefixOffset =1 << ( palette_run_prefix − 1 ) PaletteRunMinus1 = PrefixOffset +palette_run_suffix The variable PaletteRunMinus1 is used as follows: -If CopyAboveIndicesFlag[ xC ][ yC ] is equal to 0, PaletteRunMinus1specifies the number of consecutive locations minus 1 with the samepalette index. - Otherwise if palette_transpose_flag equal to 0,PaletteRunMinus1 specifies the number of consecutive locations minus 1with the same palette index as used in the corresponding position in therow above. - Otherwise, PaletteRunMinus1 specifies the number ofconsecutive locations minus 1 with the same palette index as used in thecorresponding position in the left column. When RunToEnd is equal to 0,the variable PaletteMaxRunMinus1 represents the maximum possible valuefor PaletteRunMinus1 and it is a requirement of bitstream conformancethat the value of PaletteMaxRunMinus1 shall be greater than or equal to0. palette_escape_val specifies the quantized escape coded sample valuefor a component. The variable PaletteEscapeVal[ cIdx ][ xC ][ yC ]specifies the escape value of a sample for which PaletteIndexMap[ xC ][yC ] is equal to MaxPaletteIndex and palette_escape_val_present_flag isequal to 1. The array index cIdx specifies the color component. Thearray indices xC, yC specify the location ( xC, yC ) of the samplerelative to the top-left luma sample of the picture. It is a requirementof bitstream conformance that PaletteEscapeVal[ cIdx ][ xC ][ yC ] shallbe in the range of 0 to (1 << ( BitDepth_(Y) + 1 ) ) − 1, inclusive, forcIdx equal to 0, and in the range of 0 to (1 << ( BitDepth_(C) + 1 ) ) −1, inclusive, for cIdx not equal to 0.

In the 15^(th) JVET meeting, a line-based CG is proposed (the documentnumber is JVET-O0120 and can be accessed inhttp://phenix.int-evry.fr/jvet/) to simplify the buffer usage and syntaxin the palette mode in VTM6.0. As the coefficient group (CG) used intransform coefficient coding, a CU is divided into multiple line-basedcoefficient group, each consists of m samples, where index runs, paletteindex values, and quantized colors for escape mode are encoded/parsedsequentially for each CG. As a result, pixels in a line-based CG can bereconstructed after parsing the syntax elements, e.g., index runs,palette index values, and escape quantized colors for the CG, whichhighly reduce the buffer requirement in the palette mode in VTM6.0,where the syntax elements for the whole CU have to be parsed (andstored) before reconstruction

In this application, each CU of palette mode is divided into multiplesegments of m samples (m=8 in this test) based on the traverse scanmode, as shown in FIG. 8D.

The encoding order for palette run coding in each segment is as follows:For each pixel, one context coded bin run_copy_flag=0 is signaledindicating that the pixel is of the same mode as the previous pixel,i.e., the previous scanned pixel and the current pixel are both of runtype COPY_ABOVE or the previous scanned pixel and the current pixel areboth of run type INDEX and the same index value. Otherwise,run_copy_flag=1 is signaled.

If the current pixel and the previous pixel are of different mode, onecontext coded bin copy_above_palette_indices_flag is signaled indicatingthe run type, i.e., INDEX or COPY_ABOVE, of the pixel. In this case, thedecoder does not have to parse run type if the sample is in the firstrow (horizontal traverse scan) or in the first column (vertical traversescan) since the INDEX mode is used by default. Nor does the decoder haveto parse run type if the previously parsed run type is COPY_ABOVE.

After palette run coding of pixels in one segment, the index values (forINDEX mode) and quantized escape colors are coded as bypass bins andgrouped apart from encoding/parsing of context coded bins to improvethroughput within each line-based CG. Since the index value is nowcoded/parsed after run coding, encoder does not have to signal thenumber of index values num_palette_indices minus1 and the last run typecopy_above_indices_for_final_run_flag. The syntax of the CG palette modeis illustrated in Table 4.

TABLE 4 Syntax of palette coding Descriptor palette_coding( x0, y0,cbWidth, cbHeight, startComp, numComps ) {  palettePredictionFinished =0  NumPredictedPaletteEntries = 0  for( predictorEntryIdx = 0;predictorEntryIdx < PredictorPaletteSize[ startComp ] &&  !palettePredictionFinished &&   NumPredictedPaletteEntries[ startComp] < palette_max_size; predictorEntryIdx++ ) {   palette_predictor_runae(v)   if( palette_predictor_run != 1 ) {    if(palette_predictor_run > 1 )    predictorEntryIdx += palette_predictor_run − 1   PalettePredictorEntryReuseFlags[ predictorEntryIdx ] = 1   NumPredictedPaletteEntries++   } else    palettePredictionFinished =1  }  if( NumPredictedPaletteEntries < palette_max_size )  num_signalled_palette_entries ae(v)  for( cIdx = startComp; cIdx < (startComp + numComps); cIdx++ )   for( i = 0; i <num_signalled_palette_entries; i++ )    new_palette_entries[ cIdx ][ i ]ae(v)  if( CurrentPaletteSize[ startComp ] > 0 )  palette_escape_val_present_flag ae(v)  if( MaxPaletteIndex > 0 ) {  adjust = 0   palette_transpose_flag ae(v)  }  if(treeType != DUAL_TREE_CHROMA && palette_escape_val_present_flag ) {  if( cu_qp_delta_enabled_flag && !IsCuQpDeltaCoded ) {   cu_qp_delta_abs ae(v)    if( cu_qp_delta_abs )    cu_qp_delta_sign_flag ae(v)   }  }  if( treeType != DUAL_TREE_LUMA&& palette_escape_val_present_flag ) {   if(cu_chroma_qp_offset_enabled_flag && !IsCuChromaQpOffsetCoded ) {   cu_chroma_qp_offset_flag ae(v)    if( cu_chroma_qp_offset_flag )    cu_chroma_qp_offset_idx ae(v)   }  }  PreviousRunTypePosition = 0 PreviousRunType = 0  for (subSetId = 0; subSetId <= (cbWidth* cbHeight− 1) >> 4; subSetId++) {    minSubPos = subSetId << 4    if( minSubPos +16 > cbWidth * cbHeight)     maxSubPos = cbWidth * cbHeight    else    maxSubPos = minSubPos + 16    RunCopyMap[ 0 ][ 0 ] = 0   log2CbWidth= Log2( cbWidth )    log2CbHeight = Log2( cbHeight )    PaletteScanPos =minSubPos   while( PaletteScanPos < maxSubPos ) {    xC = x0 +TraverseScanOrder[ log2CbWidth ][ log2CbHeight ][ PaletteScanPos ][  0 ]   yC = y0 + TraverseScanOrder[ log2CbWidth ][ log2CbHeight ][PaletteScanPos ][  1 ]    if( PaletteScanPos > 0 ) {     xcPrev = x0 +TraverseScanOrder[ log2CbWidth ][ log2CbHeight ][ PaletteScanPos −  1 ][0 ]     ycPrev = y0 + TraverseScanOrder[ log2CbWidth ][ log2CbHeight ][PaletteScanPos −  1 ][ 1 ]    }     if ( MaxPaletteIndex > 0 &&PaletteScanPos > 0) {      run_copy_flag ae(v)      RunCopyMap[ xC ][ yC] = run_copy_flag     }    CopyAboveIndicesFlag[ xC ][ yC ] = 0    if(MaxPaletteIndex > 0 && ! RunCopyMap[startComp][xC][yC] ) {     if( ( (!palette_transpose_flag && yC > 0 ) | | ( palette_transpose_flag && xC >0 ) )     && CopyAboveIndicesFlag[ xcPrev ][ ycPrev ] = = 0 ) {     copy_above_palette_indices_flag ae(v)      CopyAboveIndicesFlag[ xC][ yC ] = copy_above_palette_indices_flag      }      PreviousRunType =CopyAboveIndicesFlag[ xC ][ yC ]      PreviousRunTypePosition = curPos    } else {       CopyAboveIndicesFlag[ xC ][ yC ] =CopyAboveIndicesFlag[xcPrev][ycPrev]      }    }     PaletteScanPos ++  }    PaletteScanPos = minSubPos    while( PaletteScanPos < maxSubPos ){     xC = x0 + TraverseScanOrder[ log2CbWidth ][ log2CbHeight ][PaletteScanPos ][  0 ]     yC = y0 + TraverseScanOrder[ log2CbWidth ][log2CbHeight ][ PaletteScanPos ][  1 ]     if( PaletteScanPos > 0 ) {     xcPrev = x0 + TraverseScanOrder[ log2CbWidth ][ log2CbHeight ][PaletteScanPos −  1 ][ 0 ]      ycPrev = y0 + TraverseScanOrder[log2CbWidth ][ log2CbHeight ][ PaletteScanPos −  1 ][ 1 ]     }     if (MaxPaletteIndex > 0 ) {      if ( ! RunCopyMap [ x C][ yC ] &&CopyAboveIndicesFlag[ xC ][ yC ] = = 0 ) {       if( MaxPaletteIndex −adjust > 0 ) {       palette_idx_idc ae(v)       }       adjust = 1     }     }     if ( ! RunCopyMap [ xC][ yC ] && CopyAboveIndicesFlag[xC ][ yC ] = = 0 ) {       CurrPaletteIndex = palette_idx_idc     if(CopyAboveIndicesFlag[ xC ][ yC ] = = 0 ) {      PaletteIndexMap[ xC ][yC ] = CurrPaletteIndex     } else {     if ( !palette_transpose_flag )     PaletteIndexMap[ xC ][ yC ] = PaletteIndexMap[ xC ][ yC − 1 ]    else      PaletteIndexMap[ xC ][ yC ] = PaletteIndexMap[ xC − 1 ][yC ]    }   }   if( palette_escape_val_present_flag ) {    for( cIdx =startComp; cIdx < ( startComp + numComps ); cIdx++ )     for( sPos =minSubPos ; sPos < maxSubPos; sPos++ ) {      xC = x0 +TraverseScanOrder[ log2CbWidth][ log2CbHeight ][ sPos ][ 0 ]      yC =y0 + TraverseScanOrder[ log2CbWidth][ log2CbHeight ][ sPos ][ 1 ]     if( PaletteIndexMap[ cIdx ][ xC ][ yC ] = = MaxPaletteIndex ) {      palette_escape_val ae(v)       PaletteEscapeVal[ cIdx ][ xC ][ yC] = palette_escape_val     }    }   }  } }

FIG. 9 is a flowchart 900 illustrating exemplary processes by which avideo decoder decodes escape samples for a palette-mode coded codingblock in accordance with some implementations of the present disclosure.

In some embodiments, for a given block of residual samples, the kparameter values of EGk are determined according to the CU QP, denotedas QP_(CU). One specific example is illustrated as shown in Table 5below, where TH1 to TH4 are predefined thresholds satisfying(TH1<TH2<TH3<TH4), where K0 to K4 are predefined k parameter values. Itis worth noting that the same logics can be implemented differently inpractice. For example, certain equations, or a look-up table, may alsobe used to derive the same k parameters, as shown in Table 5, from a QPvalue of a current CU. In other words, the QP value here serves the dualpurposes of defining the quantization level and determining the kparameter.

TABLE 5 K parameter determination based on QP value if(QP_(CU) <TH1) { k= K0 } else if(QP_(CU) <TH2) {  k = K1 } else if(QP_(CU) <TH3) {  k =K2 } else if(QP_(CU) <TH4) {  k = K3 } else {  k = K4 }

In some embodiments, different k-th orders of Exp-Golomb binarization(e.g., k=1, 2, 3, 4, 5, etc.) may be used to derive different set ofbinary codewords for coding escape values in palette mode (e.g.,palette_escape_val). In one example, for a given block of escapesamples, the Exp-Golomb parameter used, i.e. the value of k parameter,is determined according to the QP value of the block, denoted as QPcu.The examples as illustrated in Table can be used in deriving the valueof k parameter based on a given QP value of the block. Although in thatexample four different threshold values (from TH1 to TH4) are listed,and five different k values (from K0 to K4) may be derived based onthese threshold values and QPcu, it is worth mentioning that the numberof threshold values is for illustration purpose only. In practice,different number of threshold values may be used to partition the wholeQP value range into different number of QP value segments, and for eachQP value segment, a different k value may be used to derivecorresponding binary codewords for coding escape values of a block whichis coded in palette mode. It is also worth noting that the same logicscan be implemented differently in practice. For example, certainequations, or a look-up table, may be used to derive the same kparameters.

In some embodiments, a set of the parameters and/or thresholdsassociated with the codewords determination for the syntax elements ofescape sample is signaled into the bitstream. The determined codewordsare used as binarization codewords when coding the syntax elements ofescape samples through an entropy coder, e.g. arithmetic coding.

It is noted that the set of parameters and/or thresholds can be a fullset, or a subset of all the parameters and thresholds associated withthe codewords determination for the syntax elements. The set of theparameters and/or thresholds can be signaled at different levels in thevideo bitstream. For example, they can be signaled at sequence level(e.g. the sequence parameter set), picture level (e.g. picture parameterset, and/or picture header), slice level (e.g. slice header), in codingtree unit (CTU) level or at coding unit (CU) level.

In some embodiments, the k-th orders of Exp-Golomb binarization is usedto determine the codewords for coding palette_escape_val syntax inpalette mode, and the value of k is signaled in bitstream to decoder.The value of k may be signaled at different levels, e.g. it may besignaled in slice header, picture header, PPS, and/or SPS, etc. Thesignaled Exp-Golomb parameter is used to determine the codeword forcoding the syntax palette_escape_val when a CU is coded as palette modeand the CU is associated with the above mentioned slice header, pictureheader, PPS and/or SPS, etc.

It is noted that the set of k parameters and corresponding thresholdscan be a full set, or a subset of all the k parameters and correspondingthresholds associated with the codewords determination for the syntaxelements. The set of the k parameters and corresponding thresholds canbe signaled at different levels in the video bitstream. For example,they can be signaled at sequence level (e.g., sequence parameter set),picture level (e.g., picture parameter set), slice level (e.g., sliceheader), coding tree unit (CTU) level or coding unit (CU) level.

In one example, the k parameter itself used to determine the codewordsfor coding the escape sample is signaled in the slice header, PPSheader, and/or SPS header.

To implement the above-mentioned improved process for coding escapesamples of a coding unit, video decoder 30 first receives, frombitstream, one or more syntax elements (e.g., quantization parameter(QP) values and threshold values) and video data corresponding to acoding unit encoded in palette mode (e.g., the coding unit includes oneor more escape samples) (910).

Next, video coder 30 determines a first binarization parameter (e.g.,the Exp-Golomb parameter of Exp-Golomb binarization scheme) valueaccording to the one or more syntax elements (e.g., QP values andthreshold values) (920).

The video coder 30 then decodes, from the video data, a first codewordfor an escape sample within the coding unit (930).

After decoding the first codeword, the video decoder 30 converts thefirst codeword into a value for the escape sample within the coding unitby applying the first binarization parameter to a predefinedbinarization scheme (e.g., Exp-Golomb binarization scheme) (940).

In some embodiments, the one or more syntax elements include aquantization parameter and the determining the first binarizationparameter according to the one or more syntax elements by the videocoder 30 further includes: comparing the quantization parameter with aset of thresholds, each threshold having a candidate binarizationparameter; determining a pair of thresholds covering the quantizationparameter; and determining the first binarization parameter as one ofthe two candidate binarization parameters corresponding to the pair ofthresholds.

In some embodiments, the set of thresholds and their associatedcandidate binarization parameters are constant values.

In some embodiments, the set of thresholds and their associatedcandidate binarization parameters are variables carried in the one ormore syntax elements.

In some embodiments, the one of the one or more syntax elements is thebinarization parameter.

In some embodiments, the one or more syntax elements are signaled at onelevel selected from the group consisting of sequence, picture, slice,tile, coding tree unit (CTU), coding unit (CU), transform unit (TU), andtransform block (TB).

In some embodiments, the one or more syntax elements are signaled in thebitstream.

FIG. 10 is a block diagram illustrating an example Context-adaptivebinary arithmetic coding (CABAC) engine in accordance with someimplementations of the present disclosure.

Context-adaptive binary arithmetic coding (CABAC) is a form of entropycoding used in many video coding standards, e.g., H.264/ MPEG-4 AVC,High Efficiency Video Coding (HEVC) and VVC. CABAC is based onarithmetic coding with a few changes to adapt it to the needs of videocoding standards. For example, CABAC codes binary symbols, which keepsthe complexity low and allows probability modelling for more frequentlyused bits of any symbol. Probability models are selected adaptivelybased on local context, allowing better modelling of probabilities,because coding modes are usually locally well correlated. Finally, CABACuses a multiplication-free range division by the use of quantizedprobability ranges and probability states.

CABAC has multiple probability models for different contexts. It firstconverts all non-binary symbols to binary. Then, for each bin (alsotermed “bit”), the coder selects which of the probability models to use,then uses information from nearby elements to optimize the probabilityestimate. Arithmetic coding is finally applied to compress the data.

The context modeling provides estimates of conditional probabilities ofthe coding symbols. Utilizing suitable context models, a giveninter-symbol redundancy can be exploited by switching between differentprobability models according to already-coded symbols in theneighborhood of the current symbol to encode. Coding a data symbolinvolves the following stages.

Binarization: CABAC uses Binary Arithmetic Coding which means that onlybinary decisions (1 or 0) are encoded. A non-binary-valued symbol (e.g.,a transform coefficient or motion vector) is “binarized” or convertedinto a binary code prior to arithmetic coding. This process is similarto the process of converting a data symbol into a variable length codebut the binary code is further encoded (by the arithmetic coder) priorto transmission. Stages are repeated for each bin (or “bit”) of thebinarized symbol.

Context model selection: A “context model” is a probability model forone or more bins of the binarized symbol. This model may be chosen froma selection of available models depending on the statistics of recentlycoded data symbols. The context model stores the probability of each binbeing “1” or “0”.

Arithmetic encoding: An arithmetic coder encodes each bin according tothe selected probability model. Note that there are just two sub-rangesfor each bin (corresponding to “0” and “1”).

Probability update: The selected context model is updated based on theactual coded value (e.g., if the bin value was “1”, the frequency countof “1”s is increased).

By decomposing each non-binary syntax element value into a sequence ofbins, further processing of each bin value in CABAC depends on theassociated coding-mode decision, which can be either chosen as theregular or the bypass mode. The latter is chosen for bins, which areassumed to be uniformly distributed and for which, consequently, thewhole regular binary arithmetic encoding (and decoding) process issimply bypassed. In the regular coding mode, each bin value is encodedby using the regular binary arithmetic coding engine, where theassociated probability model is either determined by a fixed choice,based on the type of syntax element and the bin position or bin index(binIdx) in the binarized representation of the syntax element, oradaptively chosen from two or more probability models depending on therelated side information (e.g., spatial neighbors, component, depth orsize of CU/PU/TU, or position within TU). Selection of the probabilitymodel is referred to as context modeling. As an important designdecision, the latter case is generally applied to the most frequentlyobserved bins only, whereas the other, usually less frequently observedbins, will be treated using a joint, typically zero-order probabilitymodel. In this way, CABAC enables selective adaptive probabilitymodeling on a sub-symbol level, and hence, provides an efficientinstrument for exploiting inter-symbol redundancies at significantlyreduced overall modeling or learning costs. Note that for both the fixedand the adaptive case, in principle, a switch from one probability modelto another can occur between any two consecutive regular coded bins. Ingeneral, the design of context models in CABAC reflects the aim to finda good compromise between the conflicting objectives of avoidingunnecessary modeling-cost overhead and exploiting the statisticaldependencies to a large extent.

The parameters of probability models in CABAC are adaptive, which meansthat an adaptation of the model probabilities to the statisticalvariations of the source of bins is performed on a bin-by-bin basis in abackward-adaptive and synchronized fashion both in the encoder anddecoder; this process is called probability estimation. For thatpurpose, each probability model in CABAC can take one out of 126different states with associated model probability values p ranging inthe interval [0:01875; 0:98125]. The two parameters of each probabilitymodel are stored as 7-bit entries in a context memory: 6 bits for eachof the 63 probability states representing the model probability pLPS ofthe least probable symbol (LPS) and 1 bit for nMPS, the value of themost probable symbol (MPS).

In one or more examples, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over, as oneor more instructions or code, a computer-readable medium and executed bya hardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the implementationsdescribed in the present application. A computer program product mayinclude a computer-readable medium.

The terminology used in the description of the implementations herein isfor the purpose of describing particular implementations only and is notintended to limit the scope of claims. As used in the description of theimplementations and the appended claims, the singular forms “a,” “an,”and “the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. It will also be understood that theterm “and/or” as used herein refers to and encompasses any and allpossible combinations of one or more of the associated listed items. Itwill be further understood that the terms “comprises” and/or“comprising,” when used in this specification, specify the presence ofstated features, elements, and/or components, but do not preclude thepresence or addition of one or more other features, elements,components, and/or groups thereof.

It will also be understood that, although the terms first, second, etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another. For example, a first electrode could be termeda second electrode, and, similarly, a second electrode could be termed afirst electrode, without departing from the scope of theimplementations. The first electrode and the second electrode are bothelectrodes, but they are not the same electrode.

The description of the present application has been presented forpurposes of illustration and description, and is not intended to beexhaustive or limited to the invention in the form disclosed. Manymodifications, variations, and alternative implementations will beapparent to those of ordinary skill in the art having the benefit of theteachings presented in the foregoing descriptions and the associateddrawings. The embodiment was chosen and described in order to bestexplain the principles of the invention, the practical application, andto enable others skilled in the art to understand the invention forvarious implementations and to best utilize the underlying principlesand various implementations with various modifications as are suited tothe particular use contemplated. Therefore, it is to be understood thatthe scope of claims is not to be limited to the specific examples of theimplementations disclosed and that modifications and otherimplementations are intended to be included within the scope of theappended claims.

What is claimed is:
 1. A method of decoding video data, the methodcomprising: receiving, from bitstream, one or more syntax elements andvideo data corresponding to a coding unit encoded in palette mode;determining a first binarization parameter according to the one or moresyntax elements; decoding, from the video data, a first codeword for anescape sample within the coding unit; and converting the first codewordinto a value for the escape sample within the coding unit by applyingthe first binarization parameter to a predefined binarization scheme. 2.The method according to claim 1, wherein the one or more syntax elementsinclude a quantization parameter and the determining the firstbinarization parameter according to the one or more syntax elementsfurther includes: comparing the quantization parameter with a set ofthresholds, each threshold having a candidate binarization parameter;determining a pair of thresholds covering the quantization parameter;and determining the first binarization parameter as one of the twocandidate binarization parameters corresponding to the pair ofthresholds.
 3. The method according to claim 2, wherein the set ofthresholds and their associated candidate binarization parameters areconstant values.
 4. The method according to claim 2, wherein the set ofthresholds and their associated candidate binarization parameters arevariables carried in the one or more syntax elements.
 5. The methodaccording to claim 1, wherein one of the one or more syntax elements isthe binarization parameter.
 6. The method according to claim 1, whereinthe one or more syntax elements are signaled at one level selected fromthe group consisting of sequence, picture, slice, tile, coding tree unit(CTU), coding unit (CU), transform unit (TU), and transform block (TB).7. The method according to claim 1, wherein the one or more syntaxelements are signaled in the bitstream.
 8. An electronic apparatuscomprising: one or more processing units; memory coupled to the one ormore processing units; and a plurality of programs stored in the memorythat, when executed by the one or more processing units, cause theelectronic apparatus to perform a method of decoding video data, themethod including: receiving, from bitstream, one or more syntax elementsand video data corresponding to a coding unit encoded in palette mode;determining a first binarization parameter according to the one or moresyntax elements; decoding, from the video data, a first codeword for anescape sample within the coding unit; and converting the first codewordinto a value for the escape sample within the coding unit by applyingthe first binarization parameter to a predefined binarization scheme. 9.The electronic apparatus according to claim 8, wherein the one or moresyntax elements include a quantization parameter and the determining thefirst binarization parameter according to the one or more syntaxelements further includes: comparing the quantization parameter with aset of thresholds, each threshold having a candidate binarizationparameter; determining a pair of thresholds covering the quantizationparameter; and determining the first binarization parameter as one ofthe two candidate binarization parameters corresponding to the pair ofthresholds.
 10. The electronic apparatus according to claim 9, whereinthe set of thresholds and their associated candidate binarizationparameters are constant values.
 11. The electronic apparatus accordingto claim 9, wherein the set of thresholds and their associated candidatebinarization parameters are variables carried in the one or more syntaxelements.
 12. The electronic apparatus according to claim 8, wherein oneof the one or more syntax elements is the binarization parameter. 13.The electronic apparatus according to claim 8, wherein the one or moresyntax elements are signaled at one level selected from the groupconsisting of sequence, picture, slice, tile, coding tree unit (CTU),coding unit (CU), transform unit (TU), and transform block (TB).
 14. Theelectronic apparatus according to claim 8, wherein the one or moresyntax elements are signaled in the bitstream.
 15. A non-transitorycomputer readable storage medium storing a plurality of programs forexecution by an electronic apparatus having one or more processingunits, wherein the plurality of programs, when executed by the one ormore processing units, cause the electronic apparatus to perform amethod of decoding video data, the method including: receiving, frombitstream, one or more syntax elements and video data corresponding to acoding unit encoded in palette mode; determining a first binarizationparameter according to the one or more syntax elements; decoding, fromthe video data, a first codeword for an escape sample within the codingunit; and converting the first codeword into a value for the escapesample within the coding unit by applying the first binarizationparameter to a predefined binarization scheme.
 16. The non-transitorycomputer readable storage medium according to claim 15, wherein the oneor more syntax elements include a quantization parameter and thedetermining the first binarization parameter according to the one ormore syntax elements further includes: comparing the quantizationparameter with a set of thresholds, each threshold having a candidatebinarization parameter; determining a pair of thresholds covering thequantization parameter; and determining the first binarization parameteras one of the two candidate binarization parameters corresponding to thepair of thresholds.
 17. The non-transitory computer readable storagemedium according to claim 16, wherein the set of thresholds and theirassociated candidate binarization parameters are constant values. 18.The non-transitory computer readable storage medium according to claim16, wherein the set of thresholds and their associated candidatebinarization parameters are variables carried in the one or more syntaxelements.
 19. The non-transitory computer readable storage mediumaccording to claim 16, wherein one of the one or more syntax elements isthe binarization parameter.
 20. The non-transitory computer readablestorage medium according to claim 16, wherein the one or more syntaxelements are signaled at one level selected from the group consisting ofsequence, picture, slice, tile, coding tree unit (CTU), coding unit(CU), transform unit (TU), and transform block (TB).